Watchdog: ‘Barebones’ FDA review of Impossible Burger discounted cancer risk

The Center for Science in the Public Interest (CSPI), calling itself “America’s food and health watchdog,” said Tuesday the U.S. Food and Drug Administration (FDA) failed to thoroughly asses the safety of a key ingredient in the plant-based Impossible Burger before approving it last month as a color additive.

The ingredient, soy leghemoglobin (SL) is a protein that contains heme, a compound also found in red meat, specifically, in the myoglobin in red meat, and blood in hemoglobin.

The World Health Organization’s International Agency for Research on Cancer (IARC) has said there is “strong evidence” that heme contributes to the carcinogenic mechanisms associated with red and processed meats.

In documents Impossible submitted to the FDA for its consideration, the company said: “Once cooked and digested, both soy leghemoglobin and animal-based myoglobin release identical heme B molecules into the digestive system.”

Armed with that information, the FDA should have required testing to determine whether the heme in soy leghemoglobin could contribute to an increase in cancer risk, Washington, D.C.-based CSPI said.

“At a minimum, it should have determined whether SL is associated with excretion of N-nitroso compounds, which is increased by heme and thought to play a role in meat-associated cancers,” the nonprofit said.

In giving a thumbs up to the safety of soy leghemoglobin (SL), the FDA did not make any reference to its guidance on recommended toxicity testing for additives used in food, CSPI said. Plus, the FDA also did not explain why it chose to ignore the guidance in approving SL as a color additive.

FDA’s guidance recommends long-term safety testing for additives like soy leghemoglobin, which fall in the agency’s highest “concern level” category due to the extent of exposure, CSPI said.

“Instead, FDA relied heavily on a short-term (28-day) study, which provides no evidence of long-term safety,” CSPI said. “FDA’s barebones review of the safety of heme excluded key endpoints well known to be associated with cancer risk and thus was inadequate under the law.”